There are various types of one-way clutch assemblies in use today. Such clutch assemblies include sprag-type, roller-type, and pawl ratchet-type assemblies. All of these one-way clutch assemblies work satisfactorily depending upon the particular application in which they are used.
In certain transmissions, increased torque capacity is needed for one-way clutch assemblies. Space constraints also require that the size of the clutch assembly be retained within certain limits. Current one-way clutch assemblies with sprags or rollers are often insufficient to add increased load carrying capacity and still maintain the space constraints.
Pawl one-way clutch assemblies can add increased nominal load capacity for a given package size. The design limits of a ratchet-type pawl clutch assembly are dictated by contact stress between the pawls and the races and/or bending, shear, and hoop stresses generated within the races.
Ratchet clutch assemblies have at least one pawl which acts to lock two notched or pocketed races together in one direction and rotate freely in the other direction. In general, the differences between known ratchet clutch assemblies relate to the control of the movement of the pawls and the effect on that movement by centrifugal forces.
Ratchet clutch assemblies are shown, for example, in U.S. Pat. Nos. 2,226,247, 3,554,340, and 5,449,057. Another ratchet clutch assembly is shown in British Patent No. 2116. The '340 patent discloses a free-wheeling bicycle hub assembly with a ratchet clutch. Under the action of centrifugal forces at high speed, the pawls can be thrown out of the joints and suffer extreme wear.
The '247 patent discloses another bicycle free-wheeling hub assembly with a ratchet clutch assembly. The pawls have a rectangular cross-section and are positioned loosely in the pockets in order to move freely. The looseness makes the position of the pawl center of mass and thus the movement of the pawl uncontrollable.
In the '057 patent, the motion of the pawls is controlled by pivoting axles that pass through the pawls. The axles are positioned on a retainer and add complexity and cost to the design. It is also difficult to position the holes in the pawls for the axles with sufficient precision for high speed operation.
In the British 2116 patent, the pawls are mounted on axles positioned on a retainer. The axles again add complexity and cost to the design. Also, centrifugal loading during high speed operation will create high forces on the axles and could adversely affect the operation of the clutch.
It is an object of the present invention to provide an improved ratchet one-way clutch assembly. It is another object of the present invention to provide an improved ratchet clutch assembly which has improved operation at high speeds.
It is still another object of the present invention to provide a ratchet one-way clutch assembly in which the pawls are provided with a tilting force or inclination toward engagement. It is a still further object of the present invention to provide a ratchet one-way clutch assembly which utilizes springs to place tilting forces on the pawls toward engagement.